# Septic System Cost: What the Code and the Parts Actually Run

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Publisher: SimplyWise, Inc. (https://www.simplywise.com)
Published: September 9, 2026
Updated: October 23, 2026
Category: Project Cost Guides
Summary: Septic system cost from the published sizing tables up: tank prices, drainfield stone, two county permit schedules, and crew wages, by bedroom count.

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## Septic System Cost: What the Code and the Parts Actually Run

Septic system cost starts with a sizing table, not a price list. Set the bedrooms and the soil below and every line updates as you type.

Size the field, price the parts

Bedrooms

Crew hours on site

Percolation rate (minutes per inch)

Snaps up to the next published row.

System type

Your permit fee ($) Fairfax County VA $425, Wake County NC $800, conventional

$3,234 to $4,517 tank, stone, permit, and crew wages

Drainfield area required780 sq ft

Trench length260 to 520 ft

Septic tank1,000 gal, $1,962 to $2,450

Drainfield stone36 tons, $435 to $812

Permit$425 to $800

Crew wages$412 to $455

Sized on Virginia’s published absorption-area table, updated Aug 28, 2026, with two county permit schedules, published tank prices, and federal wage data. Local codes and prices vary.

At a glance

1. Soil drives septic system cost. The perc rate sets the field, and the field sets everything else.
2. Virginia's Table 5.4 sizes a gravity field at 260 sq ft per bedroom at 30 minutes per inch, 1,368 at 120.
3. Virginia floors the field at 400 sq ft and the tank at 750 gallons. Other states set their own floors: North Carolina requires 1,000 gallons.
4. Poly tanks post at $1,962 to $2,450 for 1,000 gallons, $2,954 to $3,400 for 1,500.
5. Permits are public: Fairfax County VA posts $425 conventional, Wake County NC $800.
6. Crew wages run $51.44 to $56.89 an hour, operator plus laborer.

## Soil sets the price, not the house

Every septic bid starts with a perc test, because the loading tables run off it. Virginia's absorption-area table gives 260 square feet per bedroom at 30 minutes per inch and 1,368 at 120. Same house, same tank, five times the trench. That is why two bids on one street can be thousands apart.

The table floors the field at 400 square feet and the tank at 750 gallons.

## The permit is public, so quote it exactly

Fairfax County, Virginia charges $200 county plus $215 state plus a $10 indemnification fee on a new system at or under 1,000 gallons per day, and adds $200 for alternative-system plan review. Wake County, North Carolina charges $400 improvement permit plus $400 construction authorization, plus $110 design review.

## Septic system cost by bedrooms

Gravity system, 30 minute per inch soil, eight crew hours, permit band from the two counties.

| Bedrooms | Field area | Trench | Tank | Stone | Parts, permit, wages |
| --- | --- | --- | --- | --- | --- |
| 1 | 400 sq ft | 134 to 267 ft | 1,000 gal | 19 tons | $3,028 to $4,134 |
| 2 | 520 sq ft | 174 to 347 ft | 1,000 gal | 24 tons | $3,089 to $4,246 |
| 3 | 780 sq ft | 260 to 520 ft | 1,000 gal | 36 tons | $3,234 to $4,517 |
| 4 | 1,040 sq ft | 347 to 694 ft | 1,250 gal | 48 tons | $3,710 to $5,338 |
| 5 | 1,300 sq ft | 434 to 867 ft | 1,500 gal | 60 tons | $4,515 to $6,009 |

Price your own septic system job
Snap a photo on site and SimplyWise Cost Estimator turns it into an itemized estimate in about 6 seconds, with every line editable.

Free to try. Set your own prices and send the quote from the job.

Those totals cover the tank, stone, permit and crew wages only. Machine and trucking, burden, fuel, the soil evaluation, the designer, pipe, the box, risers, backfill and margin ride on top. The tank figures are one retailer's posted prices for poly tanks, read off the product pages on August 28, 2026. They are not precast concrete prices: no reachable publisher posts one.

## Turn the design into a signed quote

SimplyWise Cost Estimator turns a photo of the site into an itemized, branded estimate in about 6 seconds, with material, labor, and fee lines you can edit. Pricing is $29.99/mo or $239.99/yr, about $20/mo on annual, with a 7-day free trial.

## When the alternative system is the cheap one

Virginia defines a conventional system as a tank feeding a gravity drainfield, and an alternative system as anything else. Low pressure distribution is pumped, so it carries the higher review fee.

It also carries a smaller field. On a three bedroom house at 120 minutes per inch that is 4,104 square feet of trench under gravity against 2,052 under low pressure. The extra $200 in Fairfax or $110 in Wake buys back half the digging.

## What the trench is made of

Code, not preference. Virginia requires six inches of clean gravel or crushed stone under the percolation lines and two inches over them, where the tonnage comes from. Trenches run 18 to 36 inches wide under gravity, 8 to 24 under low pressure.

One honest gap: nobody official publishes a density or a price for washed septic stone. The tonnage converts at Wisconsin DOT's 1.85 tons per cubic yard, a dense graded base pay factor for a different rock. Confirm it with your pit.

## Price a septic install in this order

1. Get the perc rate first The soil number drives the field, the stone and the days on site.
2. Size the field from your own state table Every state publishes loading rates. Pull yours, then the minimum.
3. Pull the county fee schedule Enter yours above and the band becomes one figure.
4. Add what the calculator leaves out Machine, burden, design, pipe, backfill, margin. Parts are the floor, never the bid.

## Keep reading

- Contractor Hourly Labor Rates by Trade (2026) (https://www.simplywise.com/blog/contractor-hourly-labor-rates-by-trade/)
- How to Estimate Foundation Work: 2026 Guide (https://www.simplywise.com/blog/how-to-estimate-foundation-work/)
- Handyman Pricing: 6 Steps to Price Jobs for Profit (https://www.simplywise.com/blog/handyman-pricing-guide-maximum-profit/)
- Construction Calculators for Contractors (https://www.simplywise.com/blog/construction-calculators/)

## Sources

- Virginia 12VAC5-610-950 (https://law.lis.virginia.gov/admincode/title12/agency5/chapter610/section950/) (Table 5.4, trench widths, 400 sq ft floor; 2026-08-28).
- Virginia 12VAC5-610-930 (https://law.lis.virginia.gov/admincode/title12/agency5/chapter610/section930/) (stone depths, 2026-08-28).
- Virginia 12VAC5-610-815 (https://law.lis.virginia.gov/admincode/title12/agency5/chapter610/section815/) (Table 5.2, 2026-08-28).
- Virginia 12VAC5-613-10 (https://law.lis.virginia.gov/admincode/title12/agency5/chapter613/section10/) (definitions, 2026-08-28).
- US EPA, Types of Septic Systems (https://www.epa.gov/septic/types-septic-systems).
- Fairfax County VA, Environmental Health Fees (https://www.fairfaxcounty.gov/health/environment/fees) (2026-08-28).
- Wake County NC, Wastewater Fees (https://www.wake.gov/departments-government/onsite-water-protection/septic-system-permitting/wastewater-fees) (2026-08-28).
- Wisconsin DOT Average Unit Price List (https://wisconsindot.gov/hccidocs/contracting-info/average-unit-price.pdf) ($12.07 and $22.56 per ton).
- USGS Mineral Commodity Summaries 2026, Crushed Stone (https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-stone-crushed.pdf) ($18.50 per metric ton).
- Tank Depot, septic tanks (https://www.tank-depot.com/norwesco-102-inch-long-1000-gallon-plastic-two-compartment-septic-tank-with-two-manholes-iapmo-certified-n-41721) (Norwesco and Snyder prices; 2026-08-28).
- BLS OEWS May 2025 national file (https://www.bls.gov/oes/special-requests/oesm25nat.zip) (47-2073 and 47-2061).
- SimplyWise, Contractor Hourly Labor Rates by Trade (https://www.simplywise.com/blog/contractor-hourly-labor-rates-by-trade/).

## Common questions on septic system cost

**How much does a septic system cost to install?**

On a three bedroom house in 30 minute per inch soil, the tank, stone, permit, and crew wages run $3,234 to $4,517. Machine time, design, pipe, backfill, and margin ride on top.

**What size septic tank do I need?**

Virginia's Table 5.2 sets 750 gallons for one or two bedrooms, 900 for three, 1,200 for four and 1,500 for five, never under 750. Stocked poly sizes are 1,000, 1,250 and 1,500.

**How big does the drainfield have to be?**

It depends on the perc rate. Virginia's table runs from 165 square feet per bedroom at 5 minutes per inch to 1,368 at 120, on a 400 square foot floor.

**What does a septic permit cost?**

It depends on the county. The schedule is public. Fairfax County VA posts $425 conventional and $625 alternative. Wake County NC posts $800 and $910.

**Is an alternative septic system always more expensive?**

No. It costs more to permit, but in slow soil it needs about half the trench: on Virginia's table at 120 minutes per inch, 1,368 square feet per bedroom under gravity against 684 under low pressure. Your own state publishes its own loading rates.

**Can SimplyWise price a septic install from a photo?**

Yes. SimplyWise Cost Estimator turns a photo into an itemized estimate in about 6 seconds, with material, labor, and fee lines you can edit.

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